The invention relates to a magnetic-tape apparatus, having a frame and reel-drive means for two rotatable reels on which a magnetic tape is wound for the purpose of tape transport from one reel to the other, a length of said magnetic tape extending between the two reels. The apparatus has at least one magnetic head for recording and/or reproducing information on/from the magnetic tape, and movable tape-threading means constructed to bring the magnetic tape, which is movable between an initial position, in which the magnetic tape is not in contact with the magnetic-head means, and an operational position, in which the magnetic tape is in contact with the magnetic-head means, into said initial position or said operational position. Buffer means in the apparatus capable of buffering parts of the length of the magnetic tape comprise an endless flexible belt having two guide sections which constitute tape guides for the magnetic tape. The magnetic tape is guided over the outer sides of the guide sections, the buffer means, in said operational position, forms two tape buffers which in relation to the tape transport are situated upstream and downstream of the magnetic-head means. Movable belt-threading means bring the flexible belt, which is movable between an initial position, in which the belt is not in contact with the magnetic tape and is positioned at that side of the magnetic tape which is remote from the magnetic-head means and in which the belt-threading means are situated within the circumference of the belt, and an operational position, in which the belt is in contact with the magnetic tape in such a way that the belt can act as a buffer, into said initial position or said operational position of the belt. Tape-drive means drive the magnetic tape past the magnetic-head means at a location in that part of the tape path which is situated between the first and the last tape buffer. The apparatus also has two pairs of guide elements between which the belt is guided in its operational position, the two guide elements of each pair, viewed in the tape-transport direction, respectively define the beginning and the end of the guide sections of the belt in the operational position and guide the magnetic tape in the operational position towards and away from the guide sections, the paths of movement of the tape-threading means extending between said pairs of guide elements.
A tape-transport device for such a magnetic-tape apparatus has been proposed in U.S. application Ser. No. 496,060, filed 3/16/90, which is a continuation of Ser. No. 311,438 filed Feb. 15, 1989, now abandoned, which is a continuation of Ser. No. 024,731 filed Mar. 11, 1987, now abandoned, (herewith incorporated by reference), which aims at providing a tape-transport device in which the reel movement and the movement of the tape past the magnetic-head means are dynamically isolated from one another in such a way that strongly varying speeds of the tape past the magnetic head means can be realized with a minimal delay. This tape-transport device comprises magnetic head means and reel-drive means comprising two rotatable reels on which a magnetic tape is wound, which tape, as it is unwound, is moved in its longitudinal direction away from one of the reels with a first speed, which tape is moved passed the magnetic-head means with a second speed which is variable in magnitude relative to the first speed. The buffer means comprises an endless belt, with two tape guides which are formed by guide sections of the running belt and which control tape buffers disposed in the tape path between said reels and the magnetic-head means. The positions of the guide sections relative to the axis of rotation of the reels and the magnetic head means can be changed in order to change the length of the tape of the tape buffers, which results the reel rotations being isolated from the movement of the tape past the magnetic-head means.
Moreover, the tape transport device proposed in said Patent Application enables the magnetic head and the belt to be moved between their respective initial positions and their operational positions with the aid of movable tape and belt-threading means. In said tape-transport device the belt comprises two end portions bent through 180.degree. between which straight connecting portions are situated and in the operational position the belt is guided between two pairs of guide elements. In the operational position such a belt offers resistance to the motion movement between the guide elements because this requires some degree of elastic deformation of the belt. Moreover, owing to its shape such a belt cannot readily be positioned between the guide elements but must be inserted between the guide elements in a specific orientation.